Prop. Burnt %

[NYDAN]

I was looking through a couple of the QuickLoad projections that people have provided on this forum and I realized there was a "Prop. Burnt %" column. It got me wondering if there was any significance to that number from the reloading for accuracy perspective.

When comparing various powders for a certain caliber and bullet weight do you more experinced reloaders tend to pick powders that have a higher "Prop. Burnt %"? If a powder has a 100% Prop. Burnt % does that tend it make it more accurate?

Intuititively it seems as though if a powder burned 100% every time it would be more consistent than one that burned less than 100% every shot.

Or, is that column something that you don't pay much attention to? Do actual results not correlate to this data column?

Dan

 

[DrMike]

Excellent question, Dan. I don't select powders on the basis of percent burned. That data does inform me that the powder is burning throughout the barrel time for the projectile. It gives some indication of the shape of the pressure curve. I do, however, look at two issues--maximum chamber pressure and barrel time. I'm of the opinion that these do have an effect on accuracy. After this, I will consider the pressure curve, which describes the time to reach maximum pressure and the length of time that pressure is sustained. These give a visual estimate of what I anticipate on the previous two parameters.

 

[NYDAN]

Dr. Mike, thank you for that explanation. How does Quick load display the pressure curve? Is there one curve for one set of input parameters or will it show the pressure curve for each powder charge of a set of parameters, such as at -6.0% AND at -2.0%?

Those of you who have the program get to see these curves, whereas those of us who ask others to run data don't get to see the curves. So, there must be a real value in having your own copy of the software????

Am I correct in assuming that in your comparisons that you would like to minimize the maximum pressure and minimize the barrel time? Those would tend to be opposing trends wouldn't they?

Let me restate that as am I correct in assuming that you are looking for a low, long pressure curve and minimal barrel time?

 

[RiverRider]

Here's an example of how the pressure curve will look, Dan: